Phenotypic Screening for Small Molecules that Protect β‑Cells from Glucolipotoxicity

Type 2 diabetes is marked by progressive β-cell failure, leading to loss of β-cell mass. Increased levels of circulating glucose and free fatty acids associated with obesity lead to β-cell glucolipotoxicity. There are currently no therapeutic options to address this facet of β-cell loss in obese type 2 diabetes patients. To identify small molecules capable of protecting β-cells, we performed a high-throughput screen of 20,876 compounds in the rat insulinoma cell line INS-1E in the presence of elevated glucose and palmitate. We found 312 glucolipotoxicity-protective small molecules (1.49% hit rate) capable of restoring INS-1E viability, and we focused on 17 with known biological targets. 16 of the 17 compounds were kinase inhibitors with activity against specific families including but not limited to cyclin-dependent kinases (CDK), PI-3 kinase (PI3K), Janus kinase (JAK), and Rho-associated kinase 2 (ROCK2). 7 of the 16 kinase inhibitors were PI3K inhibitors. Validation studies in dissociated human islets identified 10 of the 17 compounds, namely, KD025, ETP-45658, BMS-536924, AT-9283, PF-03814735, torin-2, AZD5438, CP-640186, ETP-46464, and GSK2126458 that reduced glucolipotoxicity-induced β-cell death. These 10 compounds decreased markers of glucolipotoxicity including caspase activation, mitochondrial depolarization, and increased calcium flux. Together, these results provide a path forward toward identifying novel treatments to preserve β-cell viability in the face of glucolipotoxicity

Phenotypic Screening for Small Molecules that Protect β‑Cells from Glucolipotoxicity

Type 2 diabetes is marked by progressive β-cell failure, leading to loss of β-cell mass. Increased levels of circulating glucose and free fatty acids associated with obesity lead to β-cell glucolipotoxicity. There are currently no therapeutic options to address this facet of β-cell loss in obese type 2 diabetes patients. To identify small molecules capable of protecting β-cells, we performed a high-throughput screen of 20,876 compounds in the rat insulinoma cell line INS-1E in the presence of elevated glucose and palmitate. We found 312 glucolipotoxicity-protective small molecules (1.49% hit rate) capable of restoring INS-1E viability, and we focused on 17 with known biological targets. 16 of the 17 compounds were kinase inhibitors with activity against specific families including but not limited to cyclin-dependent kinases (CDK), PI-3 kinase (PI3K), Janus kinase (JAK), and Rho-associated kinase 2 (ROCK2). 7 of the 16 kinase inhibitors were PI3K inhibitors. Validation studies in dissociated human islets identified 10 of the 17 compounds, namely, KD025, ETP-45658, BMS-536924, AT-9283, PF-03814735, torin-2, AZD5438, CP-640186, ETP-46464, and GSK2126458 that reduced glucolipotoxicity-induced β-cell death. These 10 compounds decreased markers of glucolipotoxicity including caspase activation, mitochondrial depolarization, and increased calcium flux. Together, these results provide a path forward toward identifying novel treatments to preserve β-cell viability in the face of glucolipotoxicity

Effect of compounds on CD86 expression in primary CD19+ B cells.

<p>Purified human CD19+ primary B cells were incubated with 10 ng/ml IL4 alone (“No activation”) or IL4+64 ng/ml tCD40L (“Activation”), together with different concentrations of drugs for 48 hours. CD86 expression was measured by PE GeoMFI on CD19+ gated B cells. The chemical structure of each compound is shown.</p

Genetic data on risk of RA and CD40 protein levels.

<p>(A) The regional association plot from analysis of Immunochip (iChip) data in 7,222 CCP+ cases and 15,870 controls. Gene location is shown along the bottom of the graph, with observed –log(P) value along the left Y-axis and recombination rate along the right Y-axis. Each SNP is plotted is a circle, with color scheme (red to white) in reference to the extent of linkage disequilibrium with the index SNP, rs4810485 (labeled as a diamond). (B) The regional association plot from analysis of iChip data and CD40 protein levels in 90 healthy control individuals. (C) A box-whisker's plot of SNP (rs4810485) and CD40 protein levels in B cells from healthy control individuals, where T = non-risk allele and G = risk allele. (D) A box-whisker's plot of SNP (rs4810485) and <i>CD40</i> mRNA levels in PBMC's from two separate collections (total of 1,441 healthy control individuals); T = non-risk allele and G = risk allele.</p

CD40 knockdown and CD40-luciferase assay in BL2 cells.

<p>(A) Schematic of the canonical CD40 – NF-|B signaling pathway in B cells. (B) RNAi perturbation of <i>CD40</i> in two distinct clones derived from BL2 cells decreases CD40 protein levels by 55% (left) and 40% (middle) compared to the BL2 parent line (black, right); (C) More CD40 on the surface of BL2 cells increases RelA (p65) phosphorylation following activation with tCD40L, as measured by Western blot, with maximum activation at 15 minutes. Results are shown for the same two shRNA lines and parental BL2 cell line as in (B). This is a representative example of multiple experiments. (D) Titration of tCD40L leads to increased luciferase activity. Each experiment was performed in triplicate. The red circle represents ∼80% maximum luciferase activity (64 ng/ml tCD40L). Luciferase activity at baseline (i.e., no tCD40L activation) was subtracted from each measurement to plot results. (E) Titration of IKK inhibitor VII leads to inhibition of luciferase activity following tCD40L activation. Each experiment was performed in duplicate. (F) The luciferase assay is robust, with Z'-factor>0.80 and >60-fold inhibition of luciferase activity without killing cells across different plates.</p

Relative IC₅₀ for two “known” and two “novel” compounds in both BL2-NFκB-Luc and Ramos-NFκB-Luc cell lines.

<p>Relative IC₅₀ is the concentration required to bring the dose-response curve to the halfway point between the top and bottom plateaus of the curve.</p

Percent maximum inhibition for two “known” and two “novel” compounds in both BL2-NFκB-Luc and Ramos-NFκB-Luc cell lines.

<p>For each compound, we calculate the maximum amount of inhibition observed at the highest concentration of drug relative to zero luciferase activity.</p

Small molecule screen of CD40-mediated NF-kB signaling in BL2 cells.

<p>(A) Results from duplicate experiments screening 1,982 compounds. Red circles are our positive control (IKK inhibitor VII); grey circles are our neutral controls (DMSO only); and blue circles are test compounds. The red dashed line indicates >2SD from the mean of the neutral controls, which defines our “hit” compounds (n = 81 compounds). (B) Dose-response curves for two compounds known to inhibit inflammation [CID = 5282230 (tranilast)] or NF-|B signaling [CID = 5282360 (4-hydroxy-estradiol)] in the BL2-NF|B-Luc cell lines. (C) Dose-response curves for two compounds not previously implicated in inflammation, NF-κB signaling, CD40 signaling, or other biological pathways related to rheumatoid arthritis: CID = 306804, [4-(1-acetyl-4-oxo-2H-3,1-benzoxazin-2-yl)phenyl] acetate; and CID = 7309015, 8-[(Z)-3-(3,4-dimethoxyphenyl)prop-2-enoyl]-7-hydroxy-4-methylchromen-2-one. Red line = cells activated with tCD40L; black line = cells activated with either CD40 or LPS (in BL2-TLR4-NFκB-Luc cells); green line = cell toxicity, as measured by CellTiter-Glo.</p